How the environment shapes our personalities

In recent years, various research studies have shown that early life experiences can influence brain development in children. Early-life influences on brain growth and behavior were further clarified in two important studies. In an article published in the Proceedings of the National Academy of Sciences USA (PNAS), Joan Luby and colleagues reported that increased maternal support during the preschool years is associated with more rapid growth of the hippocampal region of the brain, as measured by neuroimaging. Those children with high maternal support had a two-fold increase in the rate of growth of this region when compared to children with lower levels of maternal support. The research team also demonstrated that higher rates of hippocampal growth were correlated with better emotional development.

In a separate study, published in Biological Psychiatry, Scott Mackey and colleagues studied the relationships between childhood adversity, impulsivity, patterns of brain growth, and the development of anti-social behaviours. They found that higher levels of impulsivity were associated with decreased growth in specific regions of the neocortex and increased

growth in specific subcortical brain regions. Childhood adversity influenced the growth patterns in regions of the brain thought to contribute to impulsivity, and these growth patterns were associated with the development of antisocial behaviors.

These two studies strongly suggest that environmental influences on young children have direct effects on patterns of brain maturation, which, in turn, are associated with specific

Environmental influences on young children have direct effects on patterns of brain maturation, which, in turn, are associated with specific patterns of behaviours

patterns of behaviours. The approaches used by these investigators will increasingly be employed by others to determine the roles of psychosocial influences on regional brain development in children and adolescents. Such data will enhance our understanding of the relationship between neurodevelopment, the environment, brain structures, and specific behaviors, including psychiatric illnesses.

Elucidation of structural changes associated with environmental challenges and improved methods for quantifying environmental variables may also provide measurable markers that would aid in determining the effectiveness of early interventions. For instance, would the degree of hippocampal growth in response to therapies aimed at improving maternal support be associated with better emotional development in adolescents and young adults? Would the degree of normalisation of the growth patterns in cortical and subcortical regions by specific therapies targeting impulsive behaviors minimise the development of antisocial behaviors?

Neuroimaging methods are providing increasingly sophisticated tools that are critical in advancing our understanding of normal and abnormal brain development. In addition, these methods may prove useful in predicting risks for the development of various clinical disorders and in determining the impact of intervention programmes in children at high risk for psychiatric illnesses. Many psychiatric disorders are associated with abnormal brain development. The more that we learn about the specific causes of abnormal brain development, the greater the likelihood that better treatments will be developed.

The writer is Professor and Vice-Chair for Education in the Department of Psychiatry at Washington University

Psychology Today